1. Field of the Invention
The present invention relates to a hydraulic shovel and a method of controlling a hydraulic shovel and more specifically, to a hydraulic shovel including an excavating attachment and a motor generator that assists a power supply of an engine and a method of controlling the hydraulic shovel.
2. Description of the Related Art
A hybrid shovel including an excavating attachment, an engine, a hydraulic pump driven by the engine, a hydraulic actuator driven by high pressure oil discharged from the hydraulic pump for driving the excavating attachment, and a motor generator capable of performing an assist drive operation and a power generation operation, is known (Patent Document 1).
In the hybrid shovel, a target engine speed, different from the current engine speed, is determined based on a load applied to the engine by the hydraulic pump, and the motor generator is operated to achieve the target engine speed by performing the assist drive operation or the power generation operation.
According to the hybrid shovel disclosed in Patent Document 1, with this operation, the specific fuel consumption (SFC) is improved not only at the case when the load applied to the engine by the hydraulic pump is low, but also in the case when the load applied to the engine by the hydraulic pump is large.